The semiconductor integrated circuit (IC) industry has experienced rapid growth. Over the course of the growth, functional density of the semiconductor devices has increased with decrease of device feature size or geometry. The scaling down process generally provides benefits by increasing production efficiency, reducing costs, and/or improving device performance. However, such scaling down has also increased complexity of the IC manufacturing processes.
In deep sub-micron integrated circuit technology, non-volatile memory device has become a popular storage unit due to various advantages. Particularly, the data saved in the non-volatile memory device are not lost when the power is turned off. One particular example of the non-volatile memory device includes a floating gate to retain the electrical charges associated with the saved data. However, as technologies evolve, nodes of semiconductor process have been scaled down for high density non-volatile memory device. In the manufacturing process of non-volatile memory device, further improvements are constantly necessary to satisfy the performance requirement in the scaling down process.